Extra \endgroup ... \begin{document} ... LaTeX Error: Missing \begin{document}

Question

I have basic-miktex-22.10-x on Windows 10. I saw a discussion of similar error in the Internet but did not see an answer clear for me (I am a simple user without deep understanding of the program). I have been using earlier versions of LaTeX for many years but never encountered such a problem. Help would be greatly appreciated.

\documentclass[preprint,aps,amsmath,eqsecnum,fleqn]{revtex4}
 \usepackage{bm}
 \usepackage[dvips]{graphicx}
 \newcommand{\arccosh}{\mbox{arccosh}}
 \begin{document} 
In $n$ region of the material there are charged donors and electrons excited from these donors 
 \end{document}

and texing gives

! Extra \endgroup. \document ->\endgroup \init@documenthook \set@typesize@hook \normalsize \set... l.10 \begin{document} ? ! LaTeX Error: Missing \begin{document}

Answer 1

I think that your error is due to improper use of newcommand or a not updated version of the LaTeX's distribution or a basic MikTeX (You are probably using commands that are not contained in the basic version). Here there is your full compilable example.

 \documentclass[preprint,aps,amsmath,eqsecnum,fleqn]{revtex4}
 \usepackage{bm}
 \usepackage[dvips]{graphicx}
 \DeclareMathOperator{\arccosh}{arccosh}
 \begin{document} 
In $n$ region of the material there are charged donors and electrons excited from these donors $\arccosh x=0.253$.
 \end{document}

Here there is the screenshot:

See also this link \document ->\endgroup ERROR